54 



CCELENTERATA. 



2. Calicinal or calicular gemmation. — This consists in the production 

 of buds from the calicine disc of the parent corallite, which may or may 

 not continue to grow thereafter, whilst the new corallites thus produced 

 generally repeat the process. The simplest form of calicular budding is 

 seen in some of the Rugose corals (species of Cystiphyllum, Heliophyllimi, 

 &c), where the calicine disc gives off but a single bud, which may repeat 

 the process indefinitely, till the corallum presents the appearance of a 

 succession of inverted cones placed one above the other, only the upper- 

 most of these being actually alive. It is not clear, however, that the 

 phenomena here alluded to are really the result of budding, in the proper 

 sense of the term. It is not clear, namely, that the original polype pro- 

 duces a calicine bud which kills its parent ; and another explanation of 

 the observed facts would ascribe them rather to a process of " rejuven- 

 escence " on the part of a single polype. On this view, the original polype 

 undergoes periodic contraction and partial death, only the central part 

 of the animal retaining its vitality. Each period of contraction is, how- 

 ever, followed by one of active growth, and the coral thus comes ulti- 

 mately to assume the form of a succession of inverted cones. 



In the more genuine forms of calicular budding, on the other hand, the 

 form of the corallum varies according as the buds spring from the margins 

 or centres of the calices, and as the new corallites remain free or become 

 .united with another. In one form of the process, characteristic of certain 

 Palaeozoic corals, the original polype throws up from its calicine disc one 

 or more new corallites, which kill the parent. These, in turn, produce 

 others after a similar fashion, till the entire corallum assumes the form of 

 an inverted pyramidal mass resting upon the original budding polype 



(fig- 134)- 



3. Intermural gemmation. — This mode of budding is seen in the 

 FavositidcE and in other extinct corals, and consists in the production of 



new corallites from 

 the lip of the cali- 

 cine wall of a pre- 

 existing corallite, in- 

 stead of from the 

 actual calice itself. 

 Hence in cross-sec- 

 tions of such corals 

 the new corallites 

 appear to be wedged 

 in at the angles of 

 junction of the old 

 corallites (fig. 135, a), 

 and it is not possible 

 to determine from 

 which of the tubes concerned the new bud has been given off. In long 

 sections, again, the new corallite appears as if produced by the splitting 

 of the conjoined wall of two adjacent corallites (fig. 135, b). 



4. Basal or stolonal gemmation. — This mode of increase is specially 

 characteristic of the Alcyonarians, though not confined to these. In this 

 method the original polype sends forth from its base creeping prolonga- 

 tions or "stolons" (fig. 136), from which new corallites are produced. 

 In other cases the same result is attained by the budding of new coral- 

 lites from a basal laminar expansion. In either case, the youngest coral- 

 lites are necessarily those nearest to the periphery of the colony. 



5. Fission. — Fissiparous multiplication commences by the partial 



Fig- 135. — Transverse and vertical sections of Favosites, en- 

 larged, showing intermural budding. co, A young corallite. 

 (Original.) 



